code: def aggregate(self, df):
      print(df)
      agg = pd.DataFrame.from_records(
          [{"accuracy": (df.acc_i == df.acc_l).mean()}]
      )
      return [agg]
  
file_path: NiftyNet/niftynet/evaluation/classification_evaluations.py
imports: from __future__ import absolute_import, division, print_function
  import numpy
  import pandas
  from niftynet.evaluation.base_evaluations import BaseEvaluation
  from niftynet.evaluation.base_evaluator import ScalarAggregator, DataFrameAggregator
label_desc: Use image node_id 2 for calling the accuracy obj's underlying member method code with example usage: obj.aggregate(df) and returns: list